Many consumer electronic devices are now being built with touch sensitive screens, for use with finger or stylus touch user inputs. These devices range from small screen devices such as mobile phones and car entertainment systems, to mid-size screen devices such as notebook computers, to large screen devices such as check-in stations at airports.
The present invention relates to light-based touch screens. Prior art light-based touch screens surround the screen borders with light emitters and light detectors to create a light beam grid above the screen surface. An object touching the screen from above blocks a corresponding portion of the beams.
Reference is made to FIG. 1, which is a diagram of a prior art, light-based touch screen having 16 LEDs and 16 PDs. Screen 100 in FIG. 1 is surrounded by emitters 130 along two edges and photodiode (PD) receivers 240 along the remaining two edges, which together enable a lattice of light beams covering the screen.
One drawback of prior art light-based touch screens is the need to accommodate the numerous light emitters and light detectors along all four edges of the screen. This requirement makes it difficult to insert light-based touch detection into an existing electronic device without significantly changing the layout of the device's internal components. It would be advantageous to reduce the number of components required and to enable placing them in a limited area rather than surrounding the entire screen. Reducing the total number of light emitters and light detectors required has the added benefit of reducing the bill-of-materials (BOM).